Voice-over-IP is understood in the generally accepted sense to mean telephoning via a computer network which, like the Internet, for example, is based on the foundation of the “Internet protocol”, or IP protocol for short. In the case of Voice-over-IP, the voice signals are digitized and are transmitted in the form of data packets via a “packet-oriented network” instead of via connected lines, as in a “conventional” circuit-switched telephone network such as the “landline network” or a mobile radio network.
Protocols which are used to forward digitized voice signals in IP-based computer networks are generally also called Voice-over-IP protocols. The computer networks in which Voice-over-IP telephony is made possible can also be referred to as Voice-over-IP networks.
Voice-over-IP telephony can furthermore be used only within an IP-based computer network in a company or an institution (e.g. in a local area network or in an Intranet) or else on the public Internet. The use on the public Internet is also referred to as Internet telephony in the narrower sense. For a subscriber, however, there is barely a difference between telephoning in a Voice-over-IP network and telephoning in a conventional telephone network such as the landline network or a mobile radio network.
A telephone call in a Voice-over-IP network is divided into two processes in exactly the same way as a telephone call in the landline network or in a mobile radio network, for example: setup of the connection and transmission of the call. By way of example, incoming telephone calls are forwarded to the terminal of a called Voice-over-IP subscriber—in exactly the same way as in the case of conventional telephony.
However, Voice-over-IP telephony can be used from any access facility to a Voice-over-IP network (e.g. Intranet, in-house IP-based LAN) or Internet telephony can be used from any Internet access facility by dialing up a service computer which is available on the Internet—what is known as a server, which is operated by an Internet telephony provider. This means that there is no longer a predefined association between a subscriber identification such as a subscriber telephone number and a particular geographical address—for example comprising city, road, house number, etc.—or a particular location.
In addition, what is known as an emergency call requires knowledge of the location or the geographical address of a subscriber making the emergency call. In this context, an emergency call denotes a signal which is usually sent by means of a telecommunication terminal in order to reach professional help, such as ambulance, fire brigade, police, etc. Usually, these assistance organizations can be reached on special telephone numbers—what are known as emergency numbers.
In this case, emergency numbers are special numbers in the “numbering scheme” which stipulate the sum of all specifications relating to the format and designation of dialing digits and digit combinations in telecommunication networks. Usually, these emergency numbers comprise three digits and are valid within a country for which a particular numbering scheme is defined. Emergency numbers may therefore differ from country to country. In addition, the European Union has what is known as a European emergency number—the digit combination 1-1-2—which can be used to reach professional assistance services such as ambulance, fire brigade or police in any country. The European emergency number is also used as an emergency number in mobile radio networks. Within a national area, assistance services such as ambulance, fire brigade or police can likewise be reached on the national emergency numbers (e.g. in Germany 1-1-0 for police, 1-1-2 for ambulance or fire brigade).
In addition, there may be other assistance services such as an emergency medical assistance service, breakdown services, automobile clubs, etc., which can be contacted on special telephone numbers—often likewise three-digit-numbers which are standard in the area of a country.
Since emergency numbers or telephone numbers for other assistance services are usually standard for the entire area of a country or the European Emergency call, which is valid in the entire area of the European Union, is used in mobile radio networks, it is necessary to know, for an emergency call, the location of the subscriber making the emergency call so that he can be connected to an emergency center which is closest or competent. For further assistance, it is additionally necessary to transmit to this emergency center information about the location (e.g. city, road, house number, etc.) of the subscriber making the emergency call.
According to currently applicable law, an operator of a public telephone network or a provider of telecommunication services for the public in Germany or Austria, for example, is obliged to ensure the connections to an emergency number are set up and hence routed to the respective emergency centers. For the transmission of the location data, it is currently true in Austria, for example, that a telecommunication network operator is to provide information about master data and location data only at the request of the operator of an emergency service. In this case, location data are those data which are processed in a communication network and from which the location of a telecommunication terminal belonging to a subscriber to a public communication service needs to be indicated.
In the landline network, source-dependent routing can be used for transmitting the emergency call to the closest or competent emergency center. In this case, the telephone number of the subscriber is taken and the closest or competent emergency center is ascertained, and this telephone number is then forwarded to the emergency center. By way of example, the location of the subscriber making the emergency call is then established using the transmitted telephone number of the subscriber, since the telephone number is often coupled to the address of the subscriber and hence to his location by the network operator, for example, for charging purposes.
In mobile radio networks, the emergency call is routed to the closest or competent emergency center using that radio cell to which the subscriber making the emergency call has set up a connection using his terminal, for example. With the assistance of the network operator, the emergency center can then establish the approximate location of the subscriber making the emergency call, e.g. using the position of the radio cell. More accurate position finding for the subscriber making the emergency call in a mobile radio network can be achieved by using information about signal delay time and reception field strength, and also by using new techniques such as the satellite navigation system Global Positioning System (GPS) or by means of Assisted GPS (A-GPS), for example.
For Voice-over-IP networks, although it is likewise true, according to the applicable law, that it is necessary to ensure that connections are set up to emergency numbers and routed to the respective emergency center, there is currently no regulation regarding the transmission of the location data. In Austria, for example, it is true that, provided that no location data are being processed in the operator's network—as may be the case in Voice-over-IP networks, for example—there is no legal obligation for the operator to transmit location data to the operator of an emergency service.
Efforts are therefore currently being made in Europe—in similar fashion to in the USA—to enact regulations for Voice-over-IP networks such that Voice-over-IP subscribers also reach the closest or competent emergency center among the respective emergency numbers, with information about the location of the subscriber or his terminal making the emergency call also being intended to be transmitted to the emergency center. It is therefore necessary for an association between a subscriber identification (e.g. subscriber telephone number, etc.) and location data to be made available in the Voice-over-IP network.
In Voice-over-IP networks, it is possible to distinguish between what are known as nonmobile Voice-over-IP subscribers and what are known as mobile Voice-over-IP subscribers. Nonmobile Voice-over-IP subscribers always use the same access facility (e.g. home workstation, fixed office workstation) to the Voice-over-IP network or to the Internet for the purpose of using Voice-over-IP or Internet telephony. The address (e.g. city, road, house number, etc.) of this access facility may also be referred to as the home address of the subscriber.
For these nonmobile subscribers, it is possible to use source-dependent routing for emergency calls as in the landline network, since the location of the subscriber is usually known and is not changed. To this end, subscriber data such as a subscriber identification or subscriber telephone number in the Voice-over-IP network are statically linked to routing information in order to reach the closest or competent emergency center in this way. For the purpose of localization of the subscriber, the emergency center can be sent a subscriber identification (e.g. subscriber telephone number) which is used in the emergency center to find out the location data of the subscriber making the emergency call, for example by querying a database maintained by the network operator.
In contrast, mobile Voice-over-IP subscribers are intermittently also registered at locations other than their home address when using Voice-over-IP or Internet telephony. This means that they use not only a home address (e.g. office workstation, home workstation, etc.) but also other access facilities to the Voice-over-IP network or Internet, for example—such as a second office at another location of a company, Internet access in a hotel, partial working at a home workstation, etc.
At least intermittent use of different access facilities to the Voice-over-IP or Internet means that there is no longer a fixed association between a subscriber identification, such as a subscriber telephone number, and a particular location, and the Voice-over-IP network therefore has no location data available for the mobile Voice-over-IP subscriber. It is therefore currently not possible to use source-dependent routing for emergency calls and the Voice-over-IP subscriber making the emergency call cannot be localized in the emergency center.